THINGS went from rotten to rock bottom yesterday for Christie Brinkley’s horny hubby, the demented leech called Peter Cook.

The demure supermodel took the witness stand on Day Two of this Long Island sexual farce. She sniffled. She sobbed. And she demonstrated, beyond reasonable doubt, that when a woman learns that her husband is two-timing her and masturbating for strangers on the Internet, Covergirl cosmetics do not run.

Christie, looking pale, gaunt, but impossibly pretty, testified in a breathy voice, interrupted by bouts of crying, about the moment she learned a definitive lesson: The next time Christie yearns to marry, better buy a house plant instead.

She told how the stepfather of Cook’s teen temptress, Diana Bianchi, confronted Christie after she gave a high-school graduation speech.

He asked the model to peel her hub off his little girl.

And for the first time since this pitiful drama began, Christie looked squarely in Cook’s face. She stared at him not with anger, but something a lot scarier. It was as if she saw the pathetic loser clearly for the first time.

“I looked at his face,” Christie said coldly. “It somehow explained what I knew was true.”

Then she cried.

“I was in complete shock. I couldn’t believe it. I just started driving away from the perfect life. I thought I had the picket fence. I thought we were happy.”

Meanwhile, the sum total that Cook spent on Diana Bianchi – which we learned on Wednesday was well over the $300,000 he paid for her to stay mum – continued to skyrocket. Christie found e-mails in which Diana demanded “three Gs” from Cook. She demanded he pay for her dental work, which doesn’t come cheap.

All this, for 10 or 12 rolls in the hay. Do the math, and Cook makes Eliot Spitzer look like a cheapskate.

The mistress was the least of Christie’s problems. On the Internet, “I found his naked torso with his profile underneath saying, ‘Hey, I’m a good-looking guy looking for equally good-looking girls,’ ” Christie testified. ” ‘I like them young and fit.’ ”

She found snatches of e-mails in which Peter offered to take girls shopping in exchange for sex. I’m wondering when he’ll have to register as a sexual offender.

The site he liked best was meant to match up men – older men – with younger girls, mostly. It was not a site for voyeurs, Christie said, but for real, live swingers.

“I just didn’t know who he was anymore. Who is he?” she said.

“Who is this man who sits down at my dining-room table and acts like he’s been at work? I felt really stupid. Why didn’t I know?”

The three-hanky performance was rendered even more effective on cross-examination, when Cook’s lawyer, Norman Sheresky, failed to dent her.

“You’re angry with him, aren’t you?” said the lawyer.

“I think a certain amount of anger would be perfectly normal,” said Christie. “After all, I supported this man for almost 10 years. He never paid for a single thing . . . All the while, he was carrying on like this behind my back!”

Sheresky badgered, “You are an actress, aren’t you?”

“I think that would be flattering myself, to call me an actress,” she said with a smile. “I’m trying to say I’m no Meryl Streep.

“I don’t want to flatter myself, but I was in a very successful movie, ‘National Lampoon’s Vacation.’ ”

Now coming out on DVD!

At day’s end, Christie did the worst thing she could think of to Cook: She forgave his young mistress, Diana Bianchi.

“I want her and her family to know that I feel for her,” she said. “I forgive her. She was manipulated.”

All I can say is, “Ouch!”

Give it up, Peter. You won’t get her money. Leave the kids alone. There are plenty of free chicks on the Internet.